Annual treatment can cost upwards of $35,000 and the state government is now calling on the Commonwealth to add the treatment to the Pharmaceutical Benefits Scheme.

"It's a cost beyond the realm of possibility for most families," Ms Mikakos said.

While many children are able to take anti-epileptic drugs to stop their seizures, Madison is part of the 30 per cent who continue to have seizures despite taking a cocktail of pills.

"She’s been on multiple medications, 10 different brands, 30 different tablets. They all made her feel sick, tired, lethargic," Ms Williamson said.

A known therapeutic benefit of cannabinoid products is its anti-convulsant effects. The treatment comes in oil, gel or capsule form, and is stripped of THC, the "high" component. Madison takes her dosage mixed with juice.

Royal Children's Hospital paediatric neurologist Jeremy Freeman said the treatment worked for about half the patients who tried it and for those children, the change was dramatic.

"For the patients that have a good response, the change is pretty dramatic and fairly quick. Within the first couple of months we see a major reduction in seizures," Dr Freeman said.

Madison takes 82 milligrams of the limited THC cannabis product each day. She has gone from having daily seizures to now being 10 months seizure free.

"For our family it has been life changing," Ms Williamson said.

"Now she can finish school, look for a job. If she wants, she can try go for her licence. If all goes well, there's nothing stopping her."

Mrs Williamson pleaded with the government to expand access to the scheme.

"I wish it was available to everybody," she said. "Everyone should have the opportunity to try it, see what works for them."

Ms Mikakos said the government had finished manufacturing 12 kilograms of purified crystallised cannabidiol for research and clinical trials that would be used to further the case for putting medicinal cannabis products on the PBS.

She said there had been a "maturing" of the medicinal cannabis industry in Victoria, the first state in Australia to legalise access to medicinal cannabis, and she was confident the 500-job industry would continue to grow.